Binding affinity of amyloid oligomers to cellular membranes is a generic indicator of cellular dysfunction in protein misfolding diseases

Abstract

The conversion of peptides or proteins from their soluble native states into intractable amyloid deposits is associated with a wide range of human disorders. Misfolded protein oligomers formed during the process of aggregation have been identified as the primary pathogenic agents in many such conditions. Here, we show the existence of a quantitative relationship between the degree of binding to neuronal cells of different types of oligomers formed from a model protein, HypF-N, and the GM1 content of the plasma membranes. In addition, remarkably similar behavior is observed for oligomers of the Aβ42 peptide associated with Alzheimer’s disease. Further analysis has revealed the existence of a linear correlation between the level of the influx of Ca2+ across neuronal membranes that triggers cellular damage, and the fraction of oligomeric species bound to the membrane. Our findings indicate that the susceptibility of neuronal cells to different types of misfolded oligomeric assemblies is directly related to the extent of binding of such oligomers to the cellular membrane.

A natural product inhibits the initiation of α-synuclein aggregation and suppresses its toxicity

“…3C). As we have shown previously, the toxicity caused by protein oligomers can be correlated with membrane binding (34) and this finding provides an explanation for the inhibition of the cellular damage induced by α-synuclein oligomers by squalamine and is consistent with a competitive binding model.…”

Soluble Oligomers Require a Ganglioside to Trigger Neuronal Calcium Overload

“…Alterations in membrane lipid distribution associated with an age-dependent local increase in ganglioside density and loss of cholesterol have been reported in the brain of Alzheimer's disease (AD) patients, and high-density GM1 clustering at presynaptic neuritic terminals has been shown to be a critical step in the aggregation process of amyloid-␤ peptide (A␤) [2,3]. In addition, we have recently shown the ability of GM1 to recruit oligomers grown from the 42-residue form of the amyloid-␤ peptide (A␤ 42 ) to lipid raft domains of the cell membrane [4]. These data add to, and complement, those previously reported showing the key importance of GM1 and its clusters in the neuronal membrane, not only as promoters of A␤ aggregation [5,6], but also as binding sites of A␤ oligomers [7,8].…”

“…Cell differentiation was assessed by SDS-PAGE and western blot analysis of the expression level of growth-associated protein GAP43, as previously reported [36]. The enrichment of the GM1 content was obtained by supplementing neuronal cells with 100 g/ml GM1 from bovine brain (Sigma Aldrich, Saint Louis, MO, USA) for 48 h at 37 • C, as previously described [4]. According to previous evidence in AD brains [37], the GM1 content in neuronal membranes was increased by a factor of ca.…”

“…According to previous evidence in AD brains [37], the GM1 content in neuronal membranes was increased by a factor of ca. 3, as assessed by flow cytometric analysis in conjunction with the cholera toxin subunit B (CTX-B) conjugate [4]. Cholesterol was depleted by supplementing the culture medium with ␤-cyclodextrin (␤-CD) at 2.0 mM for 30 min at 37 • C in serum-free medium [15].…”

Ultrasensitive Measurement of Ca2+ Influx into Lipid Vesicles Induced by Protein Aggregates

“…Some of these mechanisms are thought to involve specific binding to receptors on the cell membrane1, 5, 9 while others appear to be the consequence of non‐specific membrane disruption 1, 3, 5, 9, 16. A body of data suggests that small soluble aggregates, often called oligomers, rather than mature fibrils, are able to cause the membrane to become permeable to Ca 2+ resulting in Ca 2+ influx and the disruption of Ca 2+ homeostasis 2, 3, 5, 9, 17, 18. Therefore, it is important to quantify and characterize these species within aggregation mixtures in vitro as well as to be able to perform measurements in biological samples, such as cerebrospinal fluid (CSF) 19.…”